OK, so I’m not really sure what’s the deal. I bout this 96 Cherokee a week ago and was getting idle overhear. I tore down and rebuilt my cooling system (mechanical fan clutch, thermostat and housing, all 4 hoses, water pump, thermostat sensor, rear block light sensor. I’ve been getting the light coming on during idling after and when I shut the engine off, but keep the accessory on. I bought an infrared thermometer from Amazon and it seems like my temperatures are fine. It’s not happening during driving 

191 at the upper radiator hose

185 at the thermostat house

165 at the lower radiator hose

It’s hard to get a temperature read at the sender at the back of the block on the driver side. (See photo) This is the sender that triggers the light. If I take my infrared thermometer, and I measure the circular flat area on the block around where that sender screws into the block, I get 217° on this area closest to the firewall which is labeled 1. But I get 180° in the area that is pointing towards the front of the engine which is labeled 6. And then I get 232 on area labeled 3, but that is close to the manifold? I don’t know what’s accurate. 

I have the dumb cluster so I don’t have a gauge. I unplugged the thermostat mounted coolant temperature sensor (the one that doesn’t control the light) and the auxiliary fan immediately came on, it also comes on with the AC. So I am pretty convinced that it is not the electric fan. I replaced the mechanical fan clutch and all new components in the cooling system and hoses. However, I was having this problem before I even did the teardown and rebuild so I’m not really sure what it is. I don’t know where to find another sender. The part that I bought says it is for the dash with just the light, but maybe it’s calibrated to trigger at a lower temperature even though the engine is operating at normal temperature. The previous owner that I bought it from a week ago had the cooling system containing rust and crap, which is why I flushed it twice and did a whole cooling system rebuild. When I replaced the sensor in the back of the block, there was coolant all the way up to the threads, so I’m also pretty convinced that there’s not an air pocket in there somewhere. 

I’m completely at a loss and I’m not sure what to do and I’m still a little bit on the fence unsure if my engine is truly overheating since frontal temps were solid on infrared. I cannot figure it out. Again, I just have the light. And the description of this part says “with light” not lwith gauge” so I assumed I have the right part but I’ve been on the hunt for the right one and I just can’t figure it out. 

Help!

Idle Overheat